All the talk in recent years about local food has led some people to believe that's the greatest way to reduce their diet-related carbon footprint. That's wrong, and as a recent study shows, cutting out red meat (not even chicken or fish) for less than a day has the same net impact on emissions as eating a local diet 100 percent of the time. That's not to say people should stop there, since that net impact totals a mere four to five percent reduction in greenhouse gas emissions, according to the study published in the Journal of Environmental Science and Technology.

The essence of the study finds:

"Buying local" could achieve, at maximum, around a 4−5% reduction in GHG emissions due to large sources of both CO2 and non-CO2 emissions in the production of food. Shifting less than 1 day per week's (i.e., 1/7 of total calories) consumption of red meat and/or dairy to other protein sources or a vegetable-based diet could have the same climate impact as buying all household food from local providers.

In even fewer words: "dietary shift can be a more effective means of lowering an average household's food-related climate footprint than 'buying local.'"

Aside from being less than red meat, the authors don't discuss the emissions or other environmental impact of poultry or fish production, which have significant issues of their own. Poultry farms produce more ammonia emissions than oil refineries and steel mills combined, for example, and the world's oceans are being depleted of fish. But we have to start somewhere, and as the scientists have concluded, that somewhere is with red meat, which they say is about "150% more GHG-intensive than chicken or fish."

The authors also explain some of the uncertainties that couldn't be accounted for in their calculations, including land use impacts, which they say contributes an estimated 35 percent of the total GHG impact from livestock rearing. But, they continue:

While deforestation is linked to global food markets, tracing its impacts directly to consumer demand for food is a difficult task, especially given the recent confluence of biofuel and food markets; nevertheless, it should be noted that the actual climate impacts of food production are much larger than just emissions of CO2, CH4, and N2O.

Numbers people should read the study in full, as it details the methodology behind the calculations. But the takeaway is the same: eating local--for all its virtues which are not quantifiable in terms of carbon emissions alone--is one step toward reducing emissions, but it's not the most step with the most impact. To really cut down on your personal carbon footprint, cutting out meat and dairy is the way to go.